1. Field of the Invention
The present invention relates to a charging system for a vehicle having an internal combustion engine, and more particularly to a control system for a generator for a vehicle for generating power by being driven by the internal combustion engine.
2. Description of the Prior Art
A control of a generator mounted in a vehicle for generating power by being driven by the internal combustion engine of the vehicle, has generally been performed by control of a field current by using a control unit, such as a so-called IC regulator. The IC regulator detects an output voltage of a battery which is charged by an output of the generator, and supplies a field current to generate power when the output voltage becomes equal to or lower than a predetermined value, and operates to stop the power generation by cutting off the field current when the output voltage becomes higher than the predetermined value.
According to JP-A-No. 60-16195 (Mori), a control unit for a generator mounted in a vehicle controls a field current of the generator by using a microcomputer so as to perform an overall control of a power generation operation of the generator in a satisfactory manner in accordance with a state of the engine and a state of an electrical load, as well as the battery output. As is clear from an electrical circuit shown in FIG. 2 of Mori, the control unit comprising a microcomputer uses operation parameters for an internal combustion engine including sensors, etc. for detecting a turning-on of an air conditioner, head lamps, etc., to detect an operation state of the engine or a state of an electrical load. Based on the detected state of the engine operation or the detected state of the electrical load, the control unit controls the power generation of the generator mounted in the vehicle by changing over a target voltage value of a regulator for controlling the power generation in two stages.
In the latter example of the above-described control unit for a generator according to the prior-art technique, it is possible to expect a better control by the performance of an overall control of a power generation operation by detecting the state of engine operation and the state of the electrical load. However, the above method is designed merely to change over a target value of the regulator only in two stages in order to control the power generation operation of the generator. According to this method, there may easily occur variations in the number of engine revolutions and vibrations of the engine by a stepwise variation of the load of the generator during power generation, particularly during a period of an idle operation, because a rotary driving of the generator during a period of power generation works as a load for the engine. In other words, even if the above target value has been changed over, the field current is supplied if the battery voltage has not reached this target value, so that the generator is set to a power generation state, and the power generation is stopped when the target value is exceeded.